Insulated electrical connector



June 15, 1954 v, E. CARLSON INSULATED ELECTRICAL CONNECTOR Filed Jun 20,1949 I N VEN TOR.

Patented June 15, 1954 OFFICE INSULATED ELECTRICAL CONNECT-R Vernon E.Carlson, Camp Hill, Pa., assignor to Aircraft Marine Products Inc.,Harrisburg, Pa.

Application June 20, 1949, Serial No. 100,148

Claims.

This invention relates to an electrical connectorand more particularlyto electrical connec tors having tough malleable insulation permanentlysecured on the po tion which is connected to a wire and capable oftransmitting radial pressure suiiicient for forging an inner metalportion of the connector to the central conductor of "the wire.

The present invention is an improvement on the insulated terminals ofthe type set forth in the patent of William S. Watts, No. 2,410,321 andon the copending application of Robert C. Swengel,

thin metal ferrule which when applied onto the connector is to become apart of the ferrule. In cases where insulated wires with relativelythick insulation are to be used the portion of the sleeve which extendsbeyond the smaller connector fer- ,rule is required to havesubstantially larger diameter than the ferrule portion which engages thebare end of the conductor wire and consequently the plastic tubing hasto be substantially stretched in this larger insulation receiving portion. Ordinary tubing when thus applied has a greater portion ofplasticizer, in order to facilitate manufacturing operations, than canproperly be tolerated during the crimping of a connector onto a wire.After assembly, therefore, the plastic is subjected to a leaching orbaking operation to remove the excess plasticizer. During this operationthe plastic shrinks severely. Insofar as it is supported on a metalferrule this shrinking mere- ,ly gives it a tight engagement with themetal ferrule portions of the connector, but any part of the plasticsleeve which extends beyond the metal portion and which may have beensubstantially stretched may be so severely shrunken in this operation asto block off the mouth of the connector against proper entrance of theinsulated portion of the wire. This has put a limit 'on' the permissibleextension of the plastic beyond the end of the metal sleeve or ferruleespecially where the sleeve has had to be severely stretched toaccommodate the insulation, and this in turn has prevented the use ofthis type of connector in certain applications where a relatively longsparkover distance or creepage distance is required between theoutermost metal part and the nearest point on the exterior of theinsulation.

Accordingly it is an object of the present invention to overcome thedifficulties described above and to meet the requirements of such usesfor a relatively long creepage distance or sparkover path. This I haveaccomplished according to the present invention by making a relativelylong extension of the plastic material beyond the supporting metalsleeve. The long extension as set forth above tends to close in acrossthe mouth of the terminal when it is subjected to steps for removal ofexcess plasticizer. After that treatment, however, I have now found thatit is possible, even in the condition in which the plastic is left, toforce the projecting portion of the insulation inwardly so that it isinverted into the ferrule inside of the metal and then to expand itradially so that it fits against the mouth.

This I accomplished advantageously by means of a round-nosed punch asset forth more in detail hereinafter.

In the accompanying drawings I have shown, Figure l, in plan View astandard ring-tongue connector terminal embodying the present invention.

In Figure 2 I have shown in side elevation a metal sleeve covered with aplastic sleeve formed from extruded plastic tubing after shrinking ontothe metal, and Figure 3 shows an end view taken from the outer or openend of the sleeve of Figure 2.

Referring to these drawings, the ring-tongue terminal body it! includesa metal ferrule 12 which is shown in broken lines and having centralbore 14, also shown in broken lines, for reception of the-bared end ofthe central conductor of an insulated wire.

Onto the exterior ferrule I2 has been fitted a composite cover Itcomposed of an inner thin .metal ferrule is, shown in broken lines, and

exterior plastic sleeve 21]. The outer end of the composite cover isenlarged as shown to a substantially greater diameter to receive and fitover the outside of an insulated portion of the wire. Both theinsulation portion and the ferrule portion having smaller bore it areeventually pressure-forged together and together with a wire so as toform a secure and substantially perfect electrical connection.

As shown in broken lines at the left-hand end of Figure L'the end 22 ofthe plastic sleeve 20 has been inverted into the open end of the thinmetal ferrule portion is thus covering the latter and insulating it fora substantial distance.

Figure 2 shows the plastic sleeve 29 and the metal sleeve i8 in anintermediate stage of its manufacture. As shown the length of plastictubing has been stretched and pushed over the metal sleeve with asubstantial length projecting beyond the larger end of the metal sleevel8.

The insulated composite cover has then been subjected to a bakingoperation at a temperature and for a time sufiicient to remove excessplastic- 3 is then further treated by pressing into itua round-nosedpunch adapted to substantially fit the inside of the larger end ofthesleeveas shown in Figure 1. This punch may becold, but is preferablyheated to a temperature at which the plastic is substantially softened.By this means the extended end 22 of the plastic sleeve as-shown inFigures 2 and 3 is inverted and expanded to its position as shown inFigure 1.

The resulting structure has the primary advantage or insulating the endof the metal portions of the connector so as to give a desired creepagedistance .or sparkover path. In addition to this, however, it .has thefurther advantage that when the enlarged portion 18-20 is crimped ontoan insulated wire, the iii-turned plastic tube is molded into theinsulation on the wireand the insulation is forced up over its inneredge so as to give a stronger and more secure engagement than in thecase of a straight plastic sleeve not in-turned in this manner. Afurther advantage found also in the fact that the inturned plastic ifnot heated beyond a critical temperature of flow during the punchmolding operation retains elastic memory or trapped stress such that ittends very slowly to return toward the smaller diameter which .it had as.indioated in Figures 2 and 3, and this tendency may be released if thetemperature is raisedsubstantially. Any such recovery which occursincreases the pressure against the wire and thus gives a more secureconnection.

What I claim is:

1....An electrical connector of the type .comprisferrule onto a wire,which is characterized by an end of the plastic sleeve being folded backinto the end of the metal ferrule, said sleeve insulating the outer endof said ferrule inside and outside completely around its periphery andfor a substantial distance from said periphery baclc' along the insideand outside of said ferrule, said sleeve end being at least semirigidand strongly resistant to collapse or compression by forces appliedthereto along lines parallel to the axis of the sleeve and ferrulewhereby when said sleeve and ferrule ends have been compacted upon anend portion of an insulation sheath on a wire said sleeve end cannotreadily be slipped bodilyoutof said ferrule end.

2. An electrical connector of the type comprisingla metal ferrule and acovering sleeve of tough, malleable plastic material capable oftransmitting sufiicient radial pressure for cold forging the ferruleonto a wire, which is characterized by an end of the plastic sleevebeing folded back into the end of the metal ferrule; fitting closely insaid metal ferrule and having elastic memory of a smaller circumference,said sleeve insulating the outer end of said ferrule inside and outsidecompletely around its periphery and for a substantial distance from saidperiphery back along the .inside and outside of said ferrule, saidsleeve end being at least semirigid and strongly resistant to collapseor compression by forces applied thereto along lines parallel to theaxis of the sleeve and ferrule whereby when said sleeve and ferrule endshave, been compacted upon an end portion of an insulation sheath .on awire said sleeve send cannot readily be slipped bodily out of saidferrule end.

3. An electrical connector having a metal ferrule portion adapted toreceive the stripped end of the central conductor of an insulated wire,an insulation support portion of greater internal diameter than thefirst-named ferrule portion and extending beyond'said ferrule portion toreceive the insulation on said wire, and a tube of touglr' malleableplastic covering the exterior and the end of said insulation supportportion and extending back for a substantial distance entirelythroughout its periphery in intimate contact with both the inner andouter walls of said insulation support, said tube being at leastsemirigid and strongly resistant to forces of compression appliedthereto along lines parallel to the axis of the connector whereby whensaid insulation sup port portion is compressed upon an insulation sheathon a wire the portion of said tube between said insulation supportportion and such insulation sheath cannot readily he slipped bodily outof said insulation support portion.

4. The method of insulating an electrical connector ferrule whichcomprises applying onto. said ferrule a sleeve of tough malleableplastic insulation material which is substantially longer than theferrule and leaving a substantial length of said sleeve projectingbeyond the end of theferrule, shrinking the sleeve onto the ferrule,pushing back into the open end of the ferrule and eX i pending thein-turned portion of "the sleeve to :fit

against the inside of the end portion .of the ferrule.

5. An electrical connector having a metal ferrule portion adapted to becold forged into electrical contact with the center conductor of aninsulated wire, a metal insulation supporting portion secured to andextending from said.f.er rule portion and adapted to surround and becold forged into gripping relationship with the insulation covering ofsaid wire, and a continuous integral tube of deformable insulatingmaterial circumferentially covering and being in intimate contact withthe outer surface, one end,

and-a substantial annular portion adjoining said end on the interior ofsaid insulation supporting portion, said insulating tube bein of suchtough malleable material as to transmit the radial pressure by whichsaid insulation supporting portion is cold forged onto the insulationcovering 'of said wire said tube being at least semirigid and stronglyresistant to forces of compression applied thereto along lines parallelto the ax'isof the connector whereby when said tube and supportingportion are compressed upon an end portion of the insulation covering onthe wire the end of the tube cannot readily be pulled bodily out of theinterior of said insulation supporting portion.

References Cited in the file of this patent UNITED STATES PATENTS Number,Name Date 2,175,533 White Oct. 10, 1939 2,205,662 .Conradi-et al. July2 1940 2,338,316 B-uzzell Jan. 4, .1944: $2,405,111 Carlson et ,al. Aug.6,1946 2,410,321 Watts "7.-.. Oct. 29,1946 2,464,405 Knauf, Jr. Mar.vl5, .1949 2,533,200 Rogoff Dec. 5 .1950

